Pneumocandins are antifungal cyclic hexapeptides with a lipid side chain (see Schwarts et al, 1992, Journal of antibiotics, Vol 45, No 12, pages 1853-1866, Masurekar et al, 1992, Journal of Antibiotics, Vol 45, No. 12, pages 1867-1874, Hensens et al, 1992, Journal of Antibiotics, Vol 45, No 12, pages 1875-1885, Schmatz et al, 1992, Journal of Antibiotics, Vol 45, No 12, pages 1886-1891 and Adefarati et al, 1992, Journal of Antibiotics, Vol 45, No 12, pages 1953-1957 and U.S. Pat. No. 5,021,341)
The antifungal activity of Pneumocandins is connected to inhibition of the biosynthesis of 1,3β-glucans. 1,3β-glucan synthase, a multisubunit enzyme, is responsible for fungal cell wall construction, division septum deposition, and ascospore wall assembly. The catalytic subunit of this enzyme complex, an integral membrane protein, has been identified both in model yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe, and in pathogenic fungi such as Candida, Aspergillus, Cryptococcus and Pneumocystis species”. (Curr Drug Targets Infect Disord. 2001 August; 1(2):159-69 by Liu and Balasubramanian).
The Pneumocandins and Pneumocandin derivatives are useful as active pharmaceutical ingredients (APIs) and/or intermediates for producing APIs. Drugs comprising the APIs are intended for use in therapeutic or prophylactic treatment of diseases or conditions involving fungal infections.
For example, the API Caspofungin is a semi synthetic derivative of Pneumocandin B0. Caspofungin, marketed as Cancidas®, is indicated in adults and pediatric patients (3 months and older) for:                Empirical therapy for presumed fungal infections in febrile, neutropenic patients.        Treatment of Candidemia and the following Candida infections: intra-abdominal abscesses, peritonitis and pleural space infections.        Treatment of Esophageal Candidiasis.        Treatment of Invasive Aspergillosis in patients who are refractory to or intolerant of other therapies        
Thus, high purity of the API is required for safety and efficacy of the drugs.
Pneumocandin B0 can be used as a starting material for producing Caspofungin. During such production, Pneumocandin C0 will be regarded as an impurity. Thus it is desirable to monitor and control both the content of Pneumocandin B0 as well as the content of Pneumocandin C0.
Pneumocandin B0 is often produced by fermentation of the fungus Glarea lozoyensis (earlier classified as Zalerion arboricola), but many isomers and derivatives with similar physiochemical properties, are coproduced in the fermentation processes.
Pneumocandin B0 and Pneumocandin C0 are isomers which differ by the position of one hydroxyl group at a proline residue only:

Several methods for detection of Pneumocandins are known. They are however generally cumbersome and inefficient for selective detection of Pneumocandin B0 or selective detection of Pneumocandin C0. E.g., crystallization and reverse phase chromatography have been unable to separate Pneumocandin B0 from Pneumocandin C0. Normal phase chromatography utilizing ethyl acetate/methanol/water mobile phases is able to separate Pneumocandin B0 from Pneumocandin C0. This method, however, suffers from low Pneumocandin solubility in the loading solution and also from somewhat bad robustness. In addition, this mobile phase is not very compatible with mass spectrometric methods, which limits the usefulness of the method for analytical purposes.